Down-hole drilling hammer

ABSTRACT

A DOWN-HOLE DRILLING HAMMER EMBODYING AN OUTER HOUSING STRUCTURE CONNECTIBLE TO A STRING OF ROTATABLE DRILL PIPE THROUGH WHICH COMPRESSED AIR IS PUMPED. A CYLINDER SLEEVE WITHIN THE HOUSING STRUCTURE DEFINES A HIGH PRESSURE AIR ANNULUS AND A LOW AIR PRESSURE ANNULUS THEREWITH. A HAMMER PISTON RECIPROCATES IN THE CYLINDER SLEEVE, THE PISTON AND CYLINDER SLEEVE HAVING PORTS AND PASSAGES TO ALTERNATELY COMMUNICATE THE HIGH PRESSURE AND LOW PRESSURE ANNULI WITH THE CYLINDER SLEEVE FIRST ABOVE AND BELOW THE PISTON AND THEN BELOW AND ABOVE THE PISTON TO RECIPROCATE THE PISTON AND CAUSE IT TO IMPACT REPEATEDLY UPON AN ANVIL CONNECTED TO OR INTEGRAL WITH A BIT ROTATABLE BY THE DRILL STRING, THE LOW PRESSURE AIR EXHAUSTING THROUGH THE BIT TO CONVEY THE CUTTINGS UPWARDLY AROUND THE DRILLING HAMMER AND DRILL IPE TO THE DRILLING RIG.

Sept. 21, 1971 A. R. CURINGTON DOWN-HOLE DRILLING HAMMER Filed oct. e., 1969 3 Sheets-Sheet l lljllflznlc.

@LF/ago R. CUe/NGTOA/ Sept, 21, 1971 A. R. cuRlNGToN 3,606,930

DOWN-HOLE DRILLING HAMMER File? oct; e. 1969 5 Sheets-Sheell 2 16-30. .516 9b.

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N ...ILl |||L| L y, p b Q United States Patent 3,606,930 DOWN-HOLE DRILLING HAMMER Alfred R. Curington, Houston, Tex., assignor to Baker Oil Tools, Inc., City of Commerce, Calif. Filed Oct. 6, 1969, Ser. No. 863,988

Int. Cl. E21b 1/06 U.S. Cl. 173-73 22 Claims ABSTRACT OF THE DISCLOSURE A down-hole drilling hammer embodying an outer housing structure connectible to a string of rotatable drill pipe through which compressed air is pumped. A cylinder sleeve within the housing structure defines a high pressure air annulus and a low air pressure annulus therewith. A hammer piston reciprocates in the cylinder sleeve, the piston and cylinder sleeve having ports and passages to alternately communicate the high pressure and low pressure annuli with the cylinder sleeve first above and below the piston and then below and above the piston to reciprocate the piston and cause it to impact repeatedly upon an anvil connected to or integral with a bit rotatable by tte drill string, the low pressure air exhausting through the bit to convey the cuttings upwardly around the drilling hammer and drill pipe to the drilling rig.

The present invention relates to drill bit apparatus for drilling a hole in a formation, and more particularly to pneumatically operated bottom-hole drilling apparatus that imparts a percussive action to a drill bit, during which time the bit is preferably rotated.

Percussive types of drilling apparatus are known for lowering in a well bore for the purpose of drilling the hole as a result of a hammering action imposed upon a suitable bit connected to the apparatus. Prior devices are rather complex, having an arrangement of parts that limits the mass of the hammer piston which effects repeated impact blows on a coacting anvil to which the drill bit is secured or with which it is integral. The relatively light impacting pistons have a very short stroke, operating at a very high frequency. Such high frequencies produce very small cuttings, which are almost powders in consistency. The light reciprocating hammer pistons apparently are incapable of striking the anvil hard enough to break the hard formation into relatively large pieces. The prior pneumatically operated drilling apparatus require close fitting pistons and cylinders, and this fact, coupled with the extensive manufacturing operations involved in their designs, results in comparatively high manufacturing costs.

By virtue of the present invention, a pneumatically operated drilling apparatus is provided of simpler design; comparatively inexpensive to manufacture. A hammer piston is provided of greater mass than in prior devices. It has a longer stroke, thereby reducing its frequency of operation. The resulting heavier piston hammer delivers higher impact forces, and despite its lower frequency of operation achieves faster formation penetration rates. It is known that a hard formation can withstand a very high impulse load if the impulse time is very short, but the same formation will fracture at a much lower impulse force if the impulse time is increased only slightly. Thus, by virtue of the present invention,

the use of a piston of greater mass having an increased impulse time effects an increase in the penetration rate, producing much larger cuttings than resulted from the use of prior impact drilling apparatus.

With an apparatus embodying the present invention, the impact piston strikes an associated anvil during its power stroke, but it is prevented from striking any other ice portion of the tool during its return stroke. The parts are so arranged that the hammer piston is brought to rest against an air cushion, thereby preventing it from impacting upon an associated top sub, or the like. If the piston hammer were permitted to impact against such top sub, its frequency of operation would be increased, but such impacting would result in excessive tightening of threaded joints in the tool as the latter is rotated by an associated string of drill pipe during the reciprocation of the hammer piston toward and from its associated anvil.

The present invention involves a pneumatically operated down-hole percussion drill used with conventional rotary rigs equipped for air drilling medium-hard to hard formations in quarry, construction, mining and explora tion operations, and in drilling bore holes generally. The drilling hammer is of comparatively simple design, is more rugged, and is capable of drilling at much higher rates.

This invention possesses many other advantages, and has other purposes which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense.

Referring to the drawings:

FIGS. la, lb and 1c together constitute a longitudinal section through an apparatus embodying the invention with parts in their relative position for moving the ap'- paratus longitudinally in a bore hole, FIGS. 1b and 1c being lower continuations of FIGS. la and lb (respectively;

FIGS. 2a, 2b and 2c are views corresponding to FIGS. la, 1b and 1c, with the apparatus in condition for performing an impacting action against the bottom of the bore hole and with the hammer piston in its lower position, FIGS. 2b and 2c being lower continuations of FIGS. 2a and 2b, respectively;

FIGS. 3a and 3b are views corresponding to FIGS. 2li-2c, with the hammer piston in its upper position, FIG. 3b being a lower continuation of FIG. 3a;

FIG. 4 is an enlarged, fragmentary, longitudinal section through the fluid bypass portion of the apparatus; and

FIG. 5 is a cross-section taken along the line 5-5 on FIG. 1c.

The down-hole drilling -hammer A illustrated in the drawings is connected to the lower end of a string of drill pipe B extending to a drilling rig (not shown) at the top of a bore hole C, and by means of which the apparatus and a drill bit D connected to its lower end are Vrotated while compressed air or any other suitable fluid medium. is pumped down the drill pipe for operating the apparatus. The drill bit D is of any suitable type, and may have its end face tipped with tungsten carbide inserts F, for impacting against the bottom F of the bore hole while the apparatus A and bit D are being rotated, so as to impart a drilling action against the full area of the bottom of the hole as a result of an impacting action imparted to an anvil 10 integral with the drill bit or threadedly connected thereto.

The drilling hammer apparatus A includes an outer elongate housing 11, the upper end of which is threadedly connected to an upper sub 12 having an upper threaded box 13 for attachment to the lower pin 14 of an adjacent drill pipe section B. The lower end of the tubular housing is threadedly secured to a lower sub 1'5 surrounding the upper portion of the anvil 10. This sub has `drive keys 16 fitting in sub grooves 17 secured to the sub by a nut 18 threaded into the lower end of the lower sub, the keys fitting within elongate keyways 19 in the anvil 10. Accordingly, turning effort or drilling torque can be transmitted from the drill pipe B through the upper sub 12 and housing 11 to the lower sub 15, and from the lower sub to the anvil which can move longitudinally within and relative to the lower sub and housing 11, as described hereinbelow.

The upper sub 12 terminates in a head 20 closing the lower end of a central passage 21 through the upper sub, and I'which forms the upper head of a cylinder 22 that includes a cylinder sleeve 23, the upper end of which is threadedly secured to the head 20, and which extends downwardly in the housing, its lower end 24 terminating a predetermined distance above the upper end of the lower sub 15. This cylinder sleeve has an intermediate external ilange or head 25 fitting closely within the housing, this flange carrying a suitable side seal ring 26 sealingly engaging the inner wall 27 of the housing. The cylinder sleeve has a reduced diameter above and below the flange, providing an upper high pressure annular passage 28 between it and the housing, and also a lower low pressure annular passage 29 between the lower portion of the cylinder sleeve and the inner wall of the housing. This low pressure passage 29 opens into the space 30 below the sleeve 23, communicating through inlet ports 31 in the anvil with a central passage 32 in the latter that communicates with a companion passage 33 in the drill bit. The air or other uid in the passage 33 is capable of passing through the bit passages or nozzles 34, jetting against the bottom of the hole, so as to clean the hole bottom F, as well as the bit itself, of cuttings, and to flush the cuttings upwardly around the bit D and drilling apparatus A and through the annular space H between the drill pipe and wall of the bore hole to the top of the latter.

The anvil 10 terminates in an upper imperforate impact head 35 fitting snugly, but slidably, within the lower end of the cylinder sleeve 23. The impact head of the anvil is adapted to be struck by an elongate hammer piston 36 reciprocable within the cylinder sleeve 23, this piston having a longitudinal impact passage 37 opening through its upper end and communicating through a lower exhaust port 38 with an external circumferential exhaust piston groove 39. The piston also is provided with a hammer return longitudinal passage 40, opening through its lower end and communicating at the upper portion of the piston with an inlet port 41 opening into an external peripheral piston groove 42.

The cylinder sleeve 23 has one or more lower exhaust ports 43 extending between the low pressure annular passage 29 and the lower interior portion of the cylinder sleeve, and also with one or more inlet ports 44 in the upper portion of the cylinder sleeve establishing communication between the high pressure annular passage 28 and the upper portion of the interior of the cylinder sleeve. The longitudinal distance between the lower piston exhaust port 38 and the upper piston inlet port 41 is equal to the longitudinal distance between the inlet ports 44 and the exhaust ports 43. The exhaust ports 43 are so related to the upper end of the anvil 10 when the anvil is fully telescoped upwardly within the housing 11 that the lower end of the hammer piston 36 is engaging the anvil when the inlet ports 44 are aligned with the upper piston groove 42 and the exhaust ports 43 are aligned with the exhaust groove 39 at the lower portion of the piston, as disclosed in FIGS. 2a, 2b and 2c. With the piston 36 in this lower position, high pressure air can flow from the high pressure annulus 28 through the cylinder ports 44, groove 42 and piston inlet port 41 into the hammer return passage 40, passing to the lower end of the piston and exerting an upward force on the piston to shift it upwardly toward the upper cylinder head 20. At the same time, the air in the cylinder space 46 above the piston can pass 4 through the impact passage 37 and through the exhaust port 38, exhaust groove 39 and cylinder exhaust ports 43 into the low pressure annular passage 29, flowing downwardly therearound and through the anvil inlet ports 31 into its central passage 32 for discharge through the bit D.

The upper peripheral groove 42 is formed in an upper land 47 of the piston that makes a close sliding fit with the inner wall of the cylinder sleeve 23. On opposite sides of the groove 42, the land is provided with a plurality of circumferential labyrinth seal grooves 48 to inhibit leakage of fiuid between the periphery of the land and the inner wall of the cylinder sleeve. Similarly, the lower exhaust groove 39 is provided in a lower land 49 that makes a close sliding fit with the inner wall of the cylinder sleeve 23, this land also having labyrinth seal grooves 50` on opposite sides of the exhaust groove 39 for minimizing leakage of 4fiuid between the lower land and the inner wall of the cylinder sleeve. The piston has an intermediate land 51 slidably and sealingly engaging the inner wall of the cylinder and also provided with labyrinth seal' grooves 52 in its periphery to prevent leakage of fluid between the land 51 and the cylinder wall. The piston also has a reduced diameter portion 53 between the upper and intermediate lands 47, 51, to define with the cylinder wall an elongate high pressure circumferential groove 54 communicating with a side port 55 in the piston that extends from the lower portion of the groove 54 to the impact passage 37. When the piston 36 is in an elevated position, as disclosed in FIG. 3a, the high pressure groove 54 is in communication with the inlet ports 44 through the cylinder sleeve, so that high pressure air can flow through the sleeve ports 44 and high pressure groove 54 through the inlet port 55 into the impact passage 37 and into the cylinder space 46 above the piston for the purpose of driving the hammer piston 36 downwardly to strike an impact blow upon the lower anvil 10, as described hereinbelow.

The drilling hammer A is rendered inoperable unless the bit D is resting upon the bottom F of the hole C, with a required amount of drilling weight imposed upon it by the drill pipe B, acting through the upper sub 12, housing 11, lower sub 15 and nut 18, which then engages an upwardly facing shoulder 60 on the anvil 10. When the drill pipe B is elevated to raise the bit from the bottom of the hole, the anvil 10 and bit D drop downwardly, as permitted by the telescoping of the anvil within the lower sub 15, until an external anvil flange 61 engages the drive keys 16, as disclosed in FIGS. la, 1b and lc. Such lower position of the anvil 10 permits the piston 36 to drop downwardly within the cylinder sleeve 23 and expose the piston exhaust port 3-8 below the lower end of the cylinder sleeve, so that compressed air being pumped through the apparatus merely passes through the inlet ports 44 and the impact passage 37 for ilow through the exhaust port 38 into the housing space 30 below the sleeve 23, the air owing through the anvil ports 31 into its central passage 32 and then through the bit passage 33 and its nozzles 34 into the open hole. When in this position, the inlet port 41 in the upper part of the piston, communicating with the hammer return passage 40, is out of communication with the high pressure inlet ports 44, so that there is no tendency to elevate the piston within the cylinder sleeve 23. With the parts in this position, compressed air can be pumped through the apparatus to clean bit D of cuttings and impart a circulating action upwardly through the annulus H around the drill pipe B to the top of the well bore. It is only when drilling weight is imparted to the drill bit D, with the housing 11 and cylinder sleeve 23 telescoped downwardly over the anvil 10 to hold the drill blt against the bottom of the bore hole, that the apparatus becomes operatlve.

The lower side of the upper peripheral groove 42 w1ll shut off fluid flow through the ports 44 and into the hammer return passage 40 at the same time that the lower side 71 of the lower peripheral exhaust groove 39 shuts off the lower exhaust ports 43. When this occurs, high pressure air can no longer ow through the hammer return passage 40 to the lower end of the cylinder sleeve to elevate the piston 36, nor can any further air in the cylinder above the piston ow through the impact passage 37 and exhaust ports 38, 43. ln addition, the lower end 72 of the upper land 47 at the upper end of the elongate high pressure piston groove 54 will open the inlet ports 44 at the same time that the lower end 73 of the lower land 49 opens the exhaust ports 43 as a result of elevation of the piston in the cylinder sleeve. Thus, there will be communication of high pressure air with the high pressure groove 54 communicating with the impact passage 37 simultaneously with communication of the air under pressure below the piston 36 with the cylinder sleeve exhaust ports 43.

From the foregoing description, it will be noted that the upper inlet ports 44 and the lower exhaust ports 43 are simultaneously shut off from communication with the hammer return passage 40 and the impact passage 37, and that they are brought into simultaneous communication with the impact passage 37 and the hammer return passage 40 during upward travel of the piston 36 in the cylinder 22. The piston can continue travelling upwardly in the cylinder sleeve 23, but in view of the elongate high pressure passage 54 surrounding the piston, and the disposition of the lower end of the piston above the exhaust ports 43, the introduction of high pressure air into the cylinder space 46 above the piston and the exhaust of air from below the piston to the low pressure annular passage 29 continues.

In the operation of the drilling hammer, a suitable drill bit D is secured to its lower end and the drill pipe B to its upper end, whereupon it is lowered in the bore hole C. During such lowering action, the anvil is in its extended position, as shown in FIGS. la, 1b, lc, so that, if desired, compressed air can be pumped down the drill pipe B and through the apparatus A for discharge through the lower end of the drill bit D. When the drill bit contacts the bottom F of the hole, it comes to rest and the apparatus A is shifted downwardly along the anvil until the nut 18 engages the anvil shoulder 60, permitting a suitable amount of drilling weight to be imposed upon the apparatus and the bit to retain the latter in contact with the hole bottom. The drill pipe B is then rotated to rotate the bit D and compressed air at an appropriate pressure pumped down the drill pipe and into the apparatus A. At the beginning of the impacting operation of the apparatus, the hammer piston 36 will be disposed in its lower position, as illustrated in FIGS, 2a, 2b, 2c, resting upon the upper end 35 of the anvil 10 which is then disposed in sealing relation within the lower end of the cylinder sleeve 23. With the piston in this position the impact passage 37 communicates with the exhaust ports 43; whereas, the hammer return or elevating passage 40 communicates with the high pressure ports 44. Air under pressure then flows from the sub passage 21 through its side ports 21a into the high pressure annulus 28 and the piston return passage 40 to the lower end of the piston, acting upon the full cross-sectional area of the piston to shift it upwardly within the cylinder sleeve 23. As the piston is moved upwardly by the compressed air, the upper land 47 and its shoulder 70 shut off flow of the fluid through the inlet ports 44 to the return passage 40` simultaneously with the shutting olf of flow of fluid by the lower land 49 and its shoulder 71 from the cylinder space 46 above the piston 36 through the impact passage 37 and through the exhaust ports 43. At this time, the high pressure air or other gas below the piston 36 has imparted a certain amount of kinetic energy to the piston, the high pressure air below the piston expanding to continue the upward movement of the piston within the cylinder sleeve 23 and compressing the low pressure air in the cylinder kspace 46 above the piston. The piston will continue to rise in the cylinder as -a result of expansion of the high pressure air therebelow until the lower end 73 of the lower piston land 49 opens the exhaust ports 43, the inlet ports 44 being opened at the same instant, by movement of the shoulder 72 above the ports 44, to communication with the high pressure piston groove 54 that communicates with the impact passage 37. During expansion of the high pressure gas below the piston, additional kinetic energy is imparted to the piston, the high pressure air below the piston then exhausting from below the piston through the exhaust ports 43 into the low pressure annulus passage 29, from which it can ow through the anvil ports 31 and through the central anvil passage 32 and through the drill bit to Hush the cuttings from the bottom of the hole and upwardly around the bit and the annulus surrounding the drill pipe to the top of the bore hole. The piston 36 continues moving upwardly in the cylinder until its kinetic energy is overcome by the high pressure air flowing through the impact passage 37 and into the cylinder space 46 above the piston. The air trapped above the piston will have been compressed by the upward travel of the piston in the cylinder 22, but on the return or down stroke of the piston under the inuence of high pressure air in the upper portion 46 of the cylinder, the energy in the trapped air will be released and assist in propelling the piston downwardly within the cylinder. Such downward or power stroke of the piston will commence when the cornpressed air in the cylinder above the piston equals the kinetic energy of the ascending piston, reducing the kinetic energy and the velocity of the piston to zero at the top of the stroke. At this time, the piston will still be a short distance away from the upper cylinder head 20 and will be prevented from impacting thereagainst.

The high pressure air being fed into the cylinder space 46 above the piston 36 then drives the piston downwardly on its power stroke, such high pressure air being fed into the upper portion of the cylinder until the lower end 72 of the upper land 47 closes the inlet ports 44, which action will occur simultaneously with closing of the exhaust ports 43 by the lower end 73 of the lower land. However, the air pressure in the cylinder below the piston 36 is then at the low value of that existing in the low pressure annular passage 29, so that the piston can continue moving downwardly at high velocity to impact against the upper end 35 of the anvil 10.

When the piston hammer 36 strikes the anvil, the exhaust ports 43 again communicate with the impact passage 37 (FIGS. Za, 2b,- 2c), allowing the compressed air in the cylinder space above the piston to exhaust into the low pressure annular passage 29 and then through the ports 31, anvil passage 32 and drill bit passage 33, 34 into the bore hole C. At the same time, the inlet ports 44 in the sleeve 23 are again communicating with the piston return passage 40 so that high pressure air is again conducted through such passage into the cylinder sleeve 23 below the piston to again elevate the piston 36, resulting in repetition of the cycle of operation of the equip-ment.

By virtue of the drilling hammer illustrated and described, the mass of the piston 36 can be made large since it fills the entire cross-sectional area of the inner wall of the cylinder sleeve 23. There is only a slight reduction in mass due to the relatively small passages 37, 40 and ports 38, 41, 55 provided in the piston. In view of its greater mass, the piston will have a greater kinetic energy when it impacts against the anvil 1), and will, therefore, strike a greater blow against the bit D and the bottom F of the bore hole C. B :cause of its greater mass, the frequency of reciprocation of the piston 36 in the cylinder sleeve 23 will be lower than is associated with a lighter hammer piston. Such lower operational frequency is of advantage since rock fractures at a much lower impulse force if the impulse time is increased only slightly. The frequency of operation is further reduced by preventing the piston from impacting against the upper cylinder head 20 because of the cushioning action of the entrapped air abo've the 7 piston on its return stroke, the energy imparted to such trapped air being recovered during the downstroke of the piston.

The piston 36 is of relatively simple design, the only close fitting parts being between the piston and the cylinder wall. No valves or other parts are used, as in prior devices. The piston and cylinder can be manufactured through use of turning and drilling equipment, the cost of manufacture being relatively low.

If the quantity of air required for reciprocating the anvil piston is deemed insufficient for also exhausting through the apparatus for the purpose of removing the cuttings and maintaining the drill in a relatively cool and clean condition, some of the compressed air pumped down through the drill pipe B can be caused to by-pass the piston 36, so that the chips produced by the bit D can be blown from the bottom of the hole and then upy wardly towards the drilling rig. As specifically disclosed in the drawings (see FIG. 4), by-pass ports 90 are provided in the cylinder sleeve 23 immediately above its intermediate head or flange 25, which communicate with an elongate, enlargedinternal diameter portion 91 in the cylinder sleeve defining an elongate circumferential groove 92 with the exterior of the piston which extends from a position above the flange 25 to a position below the flange, where the groove communicates with a plurality of choke orifices 93 of an appropriate size or sizes in the sleeve 23 communicating with the low pressure passage 29, which will control the amount of compressed air by-passing around the flange 25 and into the low pressure annular passage, from where the compressed air will flow through the anvil ports 31 and then through the passages 32, 33, 34 through the anvil 10 and bit d to the bottom of the bore hole. Any or all of the orifices that are not needed can be rendered ineffective by threaded set screws or plugs 94 into the threaded holes 95 in the sleeve 23 extending outwardly from the orifices.

I claim:

1. In percussion drilling apparatus: an outer housing connectible to a drill string; an anvil reciprocable in the lower portion of said housing and connectible to a drill bit; a cylinder in said housing; a hammer piston reciprocable in said cylinder for intermittently impacting against said anvil; means for directing a fluid medium under pressure into said cylinder alternately at one end of said piston and then at the opposite end of said piston to reciprocate said piston in said cylinder, comprising passage means between said cylinder and housing; and means for alternately exhausting the fluid medium in said cylinder at opposite ends of said piston, including passage means in said anvil through which the fluid medium from said cylinder at one or more ends of said piston is adapted to exhaust into a fluid passage in the drill bit.

2. In apparatus as defined in claim 1; said piston shifting in said cylinder to alternately control flow of the fluid medium to said cylinder at one end of said piston and then at the opposite end of said piston.

3. In apparatus as defined in claim 1; said piston shifting in said cylinder to alternately control flow of the fluid medium to said cylinder at one end of said piston and then at the opposite end of said piston; said piston shifting in said cylinder to alternately control exhaust of the fluid medium in said cylinder first from one end of said piston and then from the opposite end of said piston.

4. In apparatus as defined in claim 1; said means for directing a fluid medium further including a passage in said piston communicable with said passage means.

5. In apparatus as defined in claim 1; said means for directing a fluid medium further including a first passage in said piston lcommunicable with said passage means to direct the fluid medium into said cylinder at one end of said piston and a second passage in said piston communicable with said passage means to direct the fluid medium into said cylinder at the opposite end of said piston.

6. In apparatus as defined in claim 1; said means for directing a fluid medium further including a first passage in said piston communicable with said passage means to direct the fluid medium into said cylinder at one end of said piston and a second passage in said piston communicable with said passage means to direct the fluid medium into said cylinder at the opposite end of said piston; said exhausting means being communicable with at least one of said passages.

7. In percussion drilling apparatus: an outer housing structure connectible to a drill string; a cylinder sleeve in said housing structure and spaced therefrom to form therewith an upper high fluid pressure passage and a lower fiuid pressure passage separate from said upper passage; an upper cylinder head closing the upper portion of said cylinder sleeve; means for conducting high pressure fluid to said upper passage; an anvil extending into the lower portion of said cylinder sleeve to close the same; a hammer piston reciprocable in said cylinder sleeve for intermittently impacting against said anvil; said cylinder sleeve having an inlet port through which fluid may flow from said upper passage into said cylinder sleeve; said cylinder sleeve having an exhaust port through which fluid may flow from said cylinder sleeve to said lower passage; said piston having a longitudinal impact passage communicating with said cylinder sleeve above said piston and communicable with said inlet port and exhaust port; said piston having a longitudinal piston return passage communicating with said cylinder sleeve below said piston and -communicable with said inlet port; said piston being reciprocable in said cylinder sleeve between a first position communicating said piston return passage with said inlet port while said impact passage communicates with said exhaust port, at which first position said piston shuts off communication between said piston return passage and exhaust port and between said impact passage and inlet port, and a second position communicating said impact passage with said inlet port while said cylinder sleeve below said piston communicates with said exhaust port, at which second position said piston shuts oil communication between said piston return passage and inlet port and between said impact passage and exhaust port.

8. In apparatus as defined in claim 7; said impact passage opening through the upper end of said piston and including an exhaust port in the lower portion of said piston communicable with said sleeve exhaust port and an inlet port in the upper portion of said piston communicating with said sleeve inlet port; said piston return passage opening through the lower end of said piston and including an upper inlet port communicating with said sleeve inlet port.

9. In apparatus as defined in claim 7; said impact passage opening through the upper end of said piston and including an exhaust port in the lower portion of said piston communicable with said sleeve exhaust port and an inlet port in the upper portion of said piston communicating with said sleeve inlet port; said piston return passage opening through the lower end of said piston and including an upper inlet port communicating with said sleeve inlet port; said return passage in'let port being located substantially above said impact passage inlet port.

10. In apparatus as defined in claim 7; said impact passage opening through the upper end of said piston and including an exhaust port in the lower portion of said piston communicable -vvith said sleeve exhaust port and an inlet port in the upper portion of said piston communicating with an elongate external piston groove communicable with said sleeve inlet port; said piston return passage opening'through the lower end of said piston and including an upper inlet port communicating with said sleeve inlet port; said return passage inlet port being located above said elongate external piston groove.

11. In apparatus as defined in claim 7; said piston being so constructed and arranged that it moves upwardly in said cylinder sleeve to simultaneously shut off communication between said impact passage and exhaust port and between said return passage and inlet port.

12. In apparatus as defined in claim 7; said piston being so constructed and arranged that it moves downwardly in said cylinder sleeve to simultaneously shut off communication between said impact passage and inlet port and between said exhaust port and cylinder sleeve below said piston.

13. In apparatus as defined in claim 7; said piston being so constructed and arranged that it moves upwardly in said cylinder sleeve to simultaneously shut off communication between said impact passage and exhaust port and between said return passage and inlet port; said piston being so constructed and arranged that it moves downwardly in said cylinder sleeve to simultaneously shut off communication between said impact passage and inlet port and between said exhaust port and cylinder sleeve below said piston.

14. In apparatus as defined in claim 7; and means providing a fluid by-pass passage between said high and Ilow pressure passages.

15. In apparatus as defined in claim 7; said impact passage opening through the upper end of said piston and including an exhaust port in the lower portion of said piston communicable with said sleeve exhaust port and an inlet port in the upper portion of said piston communicating with an elongate external piston groove communicable with said sleeve inlet port; said piston return passage opening through the lower end of said piston and including an upper inlet port communicating with said sleeve inlet port; said return passage inlet port being located above said elongate external piston groove; said piston being so constructed and arranged that it moves upwardly in said cylinder sleeve to simultaneously shut ofr communication between said impact passage and exhaust port and between said return passage and inlet port.

16. In apparatus as defined in claim 7; said impact passage opening through the upper end of said piston and including an exhaust port in the lower portion of said piston communicable with said sleeve exhaust port and an inlet port in the upper portion of said piston communicating with an elongate external piston groove communicable with said sleeve inlet port; said piston return passage opening through the lower end of said piston and including an upper inlet port communicating with said sleeve inlet port; said return passage inlet port being located above said elongate external piston groove; said piston being so constructed and arranged that it moves downwardly in said cylinder sleeve to simultaneously shut off communication between said impact passage and external piston groove and between said exhaust port and cylinder sleeve below said piston.

17. In apparatus as defined in claim 7; said impact passage opening through the upper end of said piston and including an exhaust port in the lower portion of said piston communicable with said sleeve exhaust port and an inlet port in the upper portion of said piston communicating with an elongate external piston groove communicable with said sleeve inlet port; said piston return passage opening through the lower end of said piston and including an upper inlet port communicating with said sleeve inlet port; said return passage inlet port being located above said elongate external piston groove; said piston being so constructed and arranged that it moves upwardly in said cylinder sleeve to simultaneously shut off communication between said impact passage and exhaust port and between said return passage and inlet port;

said piston being so constructed and arranged that it moves downwardly in said cylinder sleeve to simultaneously shut off communication between said impact passage and external piston groove and between said exhaust port and cylinder sleeve below said piston.

18. In apparatus as defined in claim 7; said anvil being movable from the lower portion of said cylinder sleeve to permit said piston to drop to a position in said cylinder sleeve in which the lower end of said piston is out of said cylinder sleeve and the lower portion of said impact passage is below said cylinder sleeve.

19. In percussion drilling apparatus: a housing structure having an upper connector member for securing said structure to a tubular drill string through which a fluid medium under pressure can be conducted; cylinder sleeve means having upper and lower sleeve portions in said housing structure spaced therefrom to form therewith an upper high tluid pressure passage communicable with the tubular string and a lower fluid pressure passage separate from said upper passage; an anvil extending into said lower sleeve portion and having an exhaust iluid passage communicable with said lower iluid pressure passage; a hammer piston reciprocable in said upper and lower sleeve portions for intermittently impacting against said anvil; said piston having an impact passage communicating with said upper sleeve portion above said piston and with said upper high fluid pressure passage; said piston having a return passage communicating with said lower sleeve portion below said piston and with said upper high fluid pressure passage; said piston being reciprocable in said sleeve portions to alternately control flow of fluid from said high pressure passage into said impact passage and return passage; and passage means communicating with said lower iluid pressure passage and controlled by said piston for exhausting the lluid medium from at least one of said sleeve portions to said lower fluid pressure passage.

20. In apparatus as defined in claim 19; said passage means establishing communication between said lower sleeve portion below said piston and said lower fluid pressure passage upon upward movement of said piston in said upper and lower sleeve portions.

21. In apparatus as dened in claim 19; said passage means establishing communication between said upper sleeve portion above said piston and said lower fluid pressure passage upon downward movement of said piston in said upper and lower sleeve portions.

22. In apparatus as defined in claim 19; said passage means establishing communication alternately between said upper and lower sleeve portions and said lower fluid pressure passage upon reciprocation of said piston in said upper and lower sleeve portions.

References Cited UNITED STATES PATENTS 661,786 ll/1900 Beckwith 91-234X 1,940,388 12/1933 Callahan 91--234 2,837,317 6/1958 Hulshizer 173--17 2,887,989 5/1959 Dulaney l73-17X ERNEST R. PURSER, Primary Examiner U.S. Cl. X.R.

9l`-234; l73--l7, 136 

